Metric System, Using & Converting Units June 17, 2009 Page 1 Handout: The Metric System; Using and Converting Units This handout covers the International System (SI) of units, the metric system, deriving units in the metric system, converting between both units and the metric/English systems of measurement. The SI system is the universal mathematical language of science and is based on five base units. SI Base Units Measurement SI Unit Name Symbol Alternate Unit Amount of a substance Mole mol none Length Meter m ft, in, yd, mi Mass Kilogram kg lb Temperature Kelvin K o C, o F Time Second s min, hr Chemists and other scientists perform calculations using measurements that can be very small or very large. Scientific notation makes handling these numbers easier. However, why use scientific notation if you don’t have to? This is where the metric system comes in. Metric system prefixes can often take the place of scientific notation, making calculations and keeping track of numbers that much easier. Some of the more common prefixes are shown in the table below. Metric System Prefixes Prefix Symbol Meaning Example mega M 10 6 1Mg = 10 6 g = 1000000g kilo k 10 3 1km = 1000m deka da 10 1 1daL = 10 L deci d 10-1 1ds = 0.1 s centi c 10-2 1cm = 0.01 m milli m 10-3 1mmol = 0.001 mol micro μ 10-6 1μL = 1x10-6 L nano n 10-9 1nm = 1x10-9 m Understanding numbers expressed with metric prefixes: The steps to representing measurements using metric prefixes using the following steps: • Convert your measurement to scientific notation • Find which prefix corresponds to the exponent you used • If you can’t find a prefix that matches exactly, adjust your notation so that it does • Drop the x10 number and place the corresponding prefix before the unit

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